This invention is directed generally to fiber optic splicers, and more particularly to a novel and improved re-enterable fiber optic splicer assembly adapted for splicing ends of fiber optic cables of the type used for data communications.
Re-enterable fiber optic splicer assemblies particularly designed for splicing telecommunications fiber optic cables are shown in prior U.S. Pat. Nos. 5,121,456 and 5,134,678, which are owned by the same assignee as the present invention. However, data communications fiber optic cables differ from telecommunications fiber optic cables in a number of respects. Typically, telecommunications fiber optic cables are constructed for outdoor use whereas data communications fiber optic cables are normally constructed for indoor use.
Moreover, telecommunications fiber optic cables normally comprise a relatively large number of individual optical fibers, which are bundled together in a relatively large cable having a relatively heavy, environmentally resistant and structurally strong outer jacket surrounding the entire bundle of optical fibers. The outer jacket provides the necessary structural strength for providing strain relief at points where the cable is to be clamped or otherwise held at entry/exit points to various enclosures, such as splice enclosures or the like. When the individual optical fibers are out to be spliced, the outer jacket is cut away to reveal a suitable length of optical fiber and the fibers are individually guided to splicer assemblies, for example of the type shown in the above-referenced U.S. patents, to be individually spliced or joined to optical fibers of a second similar telecommunications fiber optic cable.
In contrast, a data communications fiber optic cable typically comprises a pair of joined, individually jacketed optical fibers. Typically, each optical fiber is provided with an relatively thin inner jacket portion and an environmentally protective outer jacket therearound. Two such outer jackets connecting are joined together, much like lamp cord ("zip cord") to form a dual or duplex cable. However, neither the inner nor the outer jacket is intended as a structural member; that is, they are not intended to resist strain forces and the like applied to the cable, such as at entry or exit points of enclosures, or where the fiber is to be joined to a connector, or the like. Rather, an additional quantity of fibrous strengthening material such as a Kevlar (polyaramid) fiber is usually provided between the outer jacket and the inner jacket.
Heretofore, data communications fiber optic cables of this type have been joined by applying mating connectors to respective ends of each jacketed fiber which is to be joined. As will be more fully described below, this requires individual preparation of each cable for application of a suitable one of a pair of mating connectors, taking care to maintain a structural bond or connection between the connector and the strengthening material and also to maintain the environmental integrity of the outer jacket. However, the connectors for such fiber optic cables and the process of applying them to the cables can be relatively expensive. Moreover, once cable ends are connectorized, it is a relatively tedious process to remove the connectors and apply new connectors should some problem arise with the integrity of the connection obtained, e.g. the transmission quality across the joined connectors. Moreover, if it is desired to disconnect previously interconnected optical fibers and connect new ones, the new fibers must also be individually assembled with connectors, with the previously used connectors being unusable, thus adding further to the expense of adding or changing connections in a cabling system, for example. The use of a re-enterable splice type connection eliminates many of these problems and expenses associated with the individually connectorized jacketed optical fibers.
However, splicing a data communications cable of the foregoing type requires that the environmental protection function and integrity of the outer jacket as well as the structural function of the fibrous strengthening material be taken into account and accommodated in the structural design of the splicer assembly. In the case of the most commonly used dual or duplex type of data communications fiber optic cable, a splicer assembly must be capable of simultaneously accommodating and splicing the two optical fibers, while maintaining the above mentioned respective environmental and structural functions of the outer jackets and fibrous material associated with each of the two optical fibers.
Summarizing, in the dual or duplex type of data communications cable the outer jackets of the two fibers of the cable are physically joined along respective outer surfaces thereof. Since the cable jackets are generally circular in cross-section, the surfaces which are joined generally define a long relatively thin web along which the two outer jackets essentially abut. Thus, a problem arises in splicing a cable of this type as to how to strip back the outer jacket and fibrous strengthening material to permit access to the underlying optical fiber for splicing within a splicer assembly, while yet maintaining the environmental protective function of the outer jacket and the strengthening function of the fibrous strengthening material when the splice has been accomplished.
As an additional matter, it is difficult to properly align two fibers in a parallel side-by-side arrangement to achieve a splice between the two fibers of one duplex data communications cable and another, as described above. In this regard, it is necessary to maintain four separate elements in position simultaneously, that is, to maintain the ends of each of the two fibers of one duplex cable in alignment with the ends of the two fibers of the other duplex cable. This in turn requires that force be applied at four points within a splicing structure. Since three points define plane, it is difficult to assure that four points will be held when using a relatively rigid splicing structure.